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.TH STRERROR 3C "Aug 17, 2015"
.SH NAME
strerror, strerror_r, strerror_l \- get error message string
.SH SYNOPSIS
.LP
.nf
#include <string.h>

\fBchar *\fR\fBstrerror\fR(\fBint\fR \fIerrnum\fR);
.fi

.LP
.nf
\fBint\fR \fBstrerror_r\fR(\fBint\fR \fIerrnum\fR, \fBchar *\fR\fIstrerrbuf\fR, \fBsize_t\fR  \fIbuflen\fR);
.fi

.LP
.nf
\fBchar *\fR\fBstrerror_l\fR(\fBint\fR \fIerrnum\fR, \fBlocale_t\fR \fIloc\fR);

.SH DESCRIPTION
.LP
The \fBstrerror()\fR function maps the error number in \fIerrnum\fR to an error
message string, and returns a pointer to that string. It uses the same set of
error messages as \fBperror\fR(3C). The returned string should not be
overwritten.
.sp
.LP
The \fBstrerror_r()\fR function maps the error number in \fIerrnum\fR to
an error message string and returns the string in the buffer pointed to by
\fIstrerrbuf\fR with length \fIbuflen\fR.
.sp
.LP
The \fBstrerror_l()\fR function maps the error number in \fIerrnum\fR to
an error message string in the locale indicated by \fIloc\fR.  The
returned string should not be overwritten. If \fIloc\fR is passed the
\fBNULL\fR pointer, then the locale of the calling thread's current locale
will be used instead.
.sp
.LP
Because the \fBstrerror()\fR and \fBstrerror_l()\fR functions, return localized
strings in the event of an unknown error, one must use the value of \fBerrno\fR
to detect an error. Callers should first set \fBerrno\fR to \fB0\fR before the
call to either function and then check the value of \fBerrno\fR after the call.
If the value of \fBerrno\fR is non-zero then an error has occurred.
.SH RETURN VALUES
.LP
Upon successful completion, \fBstrerror()\fR and \fBstrerror_l()\fR return a
pointer to the generated message string. Otherwise, they set \fBerrno\fR and
returns a pointer to an error message string. They return the localized string
"Unknown error" if \fIerrnum\fR is not a valid error number.
.sp
.LP
Upon successful completion, \fBstrerror_r()\fR returns 0.  Otherwise it sets
\fBerrno\fR and returns the value of \fBerrno\fR to indicate the error. It
returns the localized string "Unknown error" in the buffer pointed to by
\fIstrerrbuf\fR if \fIerrnum\fR is not a valid error number.
.SH ERRORS
.LP
These functions may fail if:
.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The value of \fIerrnum\fR is not a valid error number.
.RE

.sp
.LP
The \fBstrerror_r()\fR function may fail if:
.sp
.ne 2
.na
\fB\fBERANGE\fR\fR
.ad
.RS 10n
The \fIbuflen\fR argument specifies insufficient storage to contain the
generated message string.
.RE

.SH USAGE
.LP
Messages returned from these functions are in the native language specified by
the \fBLC_MESSAGES\fR locale category. See \fBsetlocale\fR(3C) and
\fBuselocale\fR(3C).
.SH ATTRIBUTES
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
_
MT-Level	Safe
.TE

.SH SEE ALSO
.LP
.BR gettext (3C),
.BR perror (3C),
.BR setlocale (3C),
.BR uselocale (3C),
.BR attributes (7),
.BR standards (7)
